Accumulated evidence suggests that tumors are not uniform, but are often composed of heterogeneous cell types, subsets of which are responsible for the suppression, drug resistance, and metastasis of tumor. Such cells are referred to as cancer stem cells (or tumor-initiating cells). When cancer stem cells are targeted, it is expected to be able to treat and prevent the development, metastasis, and recurrence of cancer. However, markers defining cancer stem cells are unknown because the molecular basis of cancer stem cell phenotype remains largely unclear. In addition, no method has been established for treatment or prevention through targeting cancer stem cells.
The inventors previously demonstrated that ribophorin II (RPN2), a component of oligosaccharide transferase (OST) complex, controlled the drug resistance of breast cancer cells and that RPN2 silencing was a promising approach to overcoming the drug resistance of tumor (Patent literature 1). However, the mechanisms, such as the inhibition of cancer cell proliferation by suppressing RPN2 expression, remain unclear.